In recent years, it was reported in, for example, JP-A-5-265212 that polymers obtained from an adamantyl ester monomer have high resistance to dry etching in the process for semiconductor production. Therefore, attention is being paid to the future prospect of adamantyl ester monomer as a raw material for the resist used in semiconductor production.
The adamantyl ester monomer is generally produced by reacting an adamantane derivative (the examples thereof are shown below or the like) with a carboxylic acid compound or a derivative thereof, such as acrylic acid or methacrylic acid [hereinafter, both are referred to as (meth)acrylic acid], (meth)acrylic acid derivative or the like, to give rise to esterification.
(i) An adamantyl monool compound obtained by oxidizing adamantane or an alkyl-substituted adamantane.
(ii) An adamantyl diol compound.
(iii) A 2-alkyl-substituted-2-adamantanol compound obtained by alkylating 2-adamantanone (obtained by oxidation of adamantane) with an organometallic reagent.
Resist materials used in semiconductor production are required to have a high purity so as to be suitably used in fine processing.
Therefore, when an adamantyl ester monomer obtained by the above production process is used in a resist material for semiconductor production, the monomer need be purified in order to remove the impurities contained therein, such as metal component and the like. However, when the purification is conducted by distillation, the adamantyl ester monomer causes gelling during the distillation, which tends to incur pipe plugging and solidification in still. Therefore, it is difficult to purify the adamantyl ester monomer stably by distillation.
Thus, no method is known which can provide, from a crude adamantyl ester monomer containing impurities, an adamantyl ester monomer of high purity stably by a simple method of distillation; and development of such a method is desired.